All references cited in this specification, and their references, are incorporated by reference herein where appropriate for teachings of additional or alternative details, features, and/or technical background.
Disclosed in the embodiments herein is an image-to-sheet closed loop registration system tracking the image drum position and/or velocity and coordinating movement of the sheet into the image transfer nip based on such image drum position and/or velocity data.
The goal of a paper path system in a typical xerographic printing system is to transport media from a feeding unit in synchronism with a moving image bearing photoreceptor surface. The movement of the media to a transfer zone necessarily must arrive at the transfer zone at a given time and with a given velocity to match the velocity of the image bearing photoreceptor surface. Image forming systems involve a variety of internal components configured to manipulate a piece of paper and produce an image on the paper.
Prior art systems may comprise open loop systems with the media running at a specific speed, and position adjustment being made at a transfer registration station just prior to transfer. A difficulty with such systems is the often erratic and abrupt adjustments that must be made at the registration station due to the unpredictability of photoreceptor and media drives and the uncertainty of the position of the image on the photoreceptor. With little time and space for adjustment, the correction can be erratic. This is particularly true in higher speed, higher volume machines.
For this reason, some image forming apparatuses incorporate into the paper transporting system a mechanism for adjusting the timing of the paper reaching the image transfer position. For example, there is a construction in which, as shown in FIG. 5, two paper transporting rollers A, B are arranged along the paper transporting direction of the paper P. In this construction, the paper P fed by the paper transporting roller B on the upstream side is struck against the paper transporting roller A on the downstream side which is at rest and then the timing at which to start rotating the paper transporting roller A is adjusted to match the timing at which the paper arrives at the transfer position to the toner image arrival timing.
In order to correct for a difference in the transfer position arrival timing between the paper and the toner image. A so-called nonstop servo-registration control may be adopted which temporarily stops the paper in front of the paper transporting roller A and rotates the paper transporting roller A as the lead edge of the paper reaches the paper transporting roller A. This may eliminate possible variations in the paper engagement condition and thereby improve the precision of the paper position relative to the paper transporting roller A.
While such correction process may improve the precision of the timing of the paper arriving at the transfer position, variations in the toner image arrival timing may become a serious problem. That is, when variations in the toner image arrival timing occur, for example, due to changes in velocity of the print drum with elapse of time, it becomes difficult to match the paper arrival timing with the toner image arrival timing, even with an improved precision of the timing of the paper arriving at the transfer position. Especially in an image forming apparatus that uses an image carrying belt, such as a photosensitive belt and an intermediate transfer belt, variations in the toner image arrival timing may occur because the image carrying belt elongates or contracts in response to changes in temperature, humidity or belt tension.
FIG. 1 illustrates an image producing machine in which synchronization of the transport media from a feeding unit to the moving image on the photoreceptor surface is particularly difficult given its high speed and volume. A high-speed phase change ink image producing machine or printer 10 is illustrated. As illustrated, the machine 10 includes a frame 11 to which are mounted directly or indirectly all its operating subsystems and components. To start, the high-speed phase change ink image producing machine or printer 10 includes an imaging member 12 that is shown in the form of a drum, but can equally be in the form of a supported endless belt. The imaging member 12 has an imaging surface 14 that is movable in the direction 16, and on which phase change ink images are formed.
The high-speed phase change ink image producing machine or printer 10 also includes a phase change ink system 20 that has at least one source 22 of one color phase change ink in solid form. Since the phase change ink image producing machine or printer 10 is a multicolor image producing machine, the ink system 20 includes for example four (4) sources 22, 24, 26, 28, representing four (4) different colors CYMK (cyan, yellow, magenta, black) of phase change inks. The phase change ink system 20 also includes a phase change ink melting and control assembly 100 (FIG. 2), for melting or phase changing the solid form of the phase change ink into a liquid form. Thereafter, the phase change ink melting and control assembly 100 then controls and supplies the molten liquid form of the ink towards a printhead system 30 including at least one printhead assembly 32. Since the phase change ink image producing machine or printer 10 is a high-speed, or high throughput, multicolor image producing machine, the printhead system includes for example four (4) separate printhead assemblies 32, 34, 36 and 38 as shown.
As further shown, the phase change ink image producing machine or printer 10 includes a substrate supply and handling system 40. The substrate supply and handling system 40 for example may include substrate supply sources 42, 44, 46, 48, of which supply source 48 for example is a high capacity paper supply or feeder for storing and supplying image receiving substrates in the form of cut sheets for example. The substrate supply and handling system 40 in any case includes a substrate handling and treatment system 50 that has a substrate pre-heater 52, substrate and image heater 54, and a fusing device 60. The phase change ink image producing machine or printer 10 as shown may also include an original document feeder 70 that has a document holding tray 72, document sheet feeding and retrieval devices 74, and a document exposure and scanning system 76.
Operation and control of the various subsystems, components and functions of the machine or printer 10 are performed with the aid of a controller or electronic subsystem 80. The electronic subsystem or controller 80 for example is a self-contained, dedicated mini-computer having a central processor unit 82, electronic storage 84, and a display or user interface 86. The electronic subsystem or controller 80 for example includes sensor input and control means 88 as well as a pixel placement and control means 89. In addition the central processing unit 82 reads, captures, prepares and manages the image data flow between image input sources such as the scanning system 76, or an online or a work station connection 90, and the printhead assemblies 32, 34, 36, 38. As such, the electronic subsystem or controller 80 is the main multi-tasking processor for operating and controlling all of the other machine subsystems and functions, including the machine's printing operations.
In operation, image data for an image to be produced is sent to the controller 80 from either the scanning system 76 or via the online or work station connection 90 for processing and output to the printhead assemblies 32, 34, 36, 38. Additionally, the controller determines and/or accepts related subsystem and component controls, for example from operator inputs via the user interface 86, and accordingly executes such controls. As a result, appropriate color solid forms of phase change ink are melted and delivered to the printhead assemblies. Additionally, pixel placement control is exercised relative to the imaging surface 14 thus forming desired images per such image data, and receiving substrates are supplied by anyone of the sources 42, 44, 46, 48 and handled by means 50 in timed registration with image formation on the surface 14. Finally, the image is transferred within the transfer nip 92, from the surface 14 onto the receiving substrate for subsequent fusing at fusing device 60.